It is an excerpt from Capt. Robert Falcon Scott letter "To: my widow" which he wrote while dying in Antarctic:
"Had we lived, I should have had a tale to tell of the hardihood, endurance, and courage of my companions which would have stirred the heart of every Englishman. These rough notes and our dead bodies must tell the tale."
It seems that a complex structure of "Had we lived, I should have had a story to tell" exhibits nuances which the author wanted to express. Can anyone please explain what the phrase means and which nuances does it possess?